The boat sailed at a speed of 18 km / h during the first hour. In the second hour he reduced the speed by 15%, and in the third hour he increased the speed by 20%. What is the speed of the boat?
We find by how many km / h the boat reduced its speed in the second hour.
To do this, multiply the initial speed of the boat by the percentage.
18 * 15% / 100% = 18 * 0.15 = 2.7 km / h.
In this case, the speed of the boat at 2 o’clock was:
18 – 2.7 = 15.3 km / h.
After the boat increased its speed by 20%, it increased by:
15.3 * 20% / 100% = 15.3 * 0.2 = 3.06 km / h.
From this it follows that the new speed was equal to:
15.3 + 3.06 = 18.36 km / h.
Answer: 18.36 km / h.
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